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Method of manufacturing a MEMS structure and use of the method

a manufacturing method and technology of mems structure, applied in the direction of microstructural devices, instruments, coatings, etc., can solve the problems of poor dimensional precision in the structure, quadrature signal, and quadrature errors, and achieve the effect of eliminating non-uniformities within the wafer

Active Publication Date: 2015-11-26
MURATA MFG CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention provides a structure for compensating for non-uniformities in a wafer using improved methods. This simplifies the process of compensating for quadrature signals.

Problems solved by technology

The production process and the technology used for producing the structures with the springs and the beams in MEMS based gyroscopes often lead to quadrature errors, i.e. errors caused by driving the vibrating proof mass along a direction which is not exactly perpendicular to the direction along which the Coriolis movement is measured.
One of the most significant problems in micromechanical vibrating sensors of angular velocity is the so called quadrature signal, which is caused by poor dimensional precision in the structures.
Compensation by means of electric forces, however, constitutes a challenge to the sensor's electronics requiring either accurate phase control or, possibly, large voltages and separate structures within the sensor.
A typical non-ideality in especially Deep Reactive Ion Etched (DRIE) structures causing problems is that some etches undercut the masking layer and form trenches with sloping sidewalls.
The undercut problem is even more difficult to solve if its extent varies within the structure.
However, the biasing of the mask does not provide a complete solution because the DRIE undercut varies across the wafer.

Method used

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  • Method of manufacturing a MEMS structure and use of the method
  • Method of manufacturing a MEMS structure and use of the method
  • Method of manufacturing a MEMS structure and use of the method

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first embodiment

[0095]The first embodiment alternative, presented by FIGS. 4a-4d, is an etch-back procedure, wherein a part of the masking material deposited as a trench filling 4 is chemically removed to reveal top surface of the structures 1.

[0096]In the first embodiment, FIG. 4a (correspondingly to FIGS. 2i and 2j) shows the fifth step of the method of the invention, wherein a third mask 5 is deposited on the silicon dioxide trench filling 4 on selected areas where etching is not allowed.

[0097]In the next and sixth step, as illustrated by FIG. 4b (correspondingly to FIGS. 2k and 2l), a part of the masking material filling 4 is removed using some suitable technique such as lithography and etch back. The third mask 5 protects the masking material filling 4 on areas defining the final structure and where final structure etching is not allowed.

[0098]FIG. 4c (correspondingly to FIGS. 2m-2n) shows a DRIE etch step for making the final structures as the seventh step of the method of the invention. The ...

second embodiment

[0101]In the second embodiment alternative, presented by FIGS. 5a-5d, Chemical Mechanical Polishing / Planarization (CMP) is used to smooth the surface of the wafer and remove filling 4 on areas to be etched. The remaining filling 4′ left fills the trenches 3a as shown by FIG. 5a. Chemical Mechanical Polishing / Planarization is a process of smoothing surfaces with the combination of chemical and mechanical forces. It can be thought of as a hybrid of chemical etching and free abrasive polishing. The fifth step presented by FIG. 5a uses the above mentioned CMP process to smooth the surface of the wafer, whereby a part of the silicon dioxide layer 4 is left deposited on the wafer as a remaining filling 4′ in the shape of trenches 3a.

[0102]Not until thereafter, in the sixth step of the second embodiment as presented by FIG. 5b, a third mask 5 is deposited as an intermediate mask for defining the final structure in order to protect areas where etching for finals structures is not allowed.

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Abstract

A method creates MEMS structures by selectively etching a silicon wafer that is patterned by using a masking layer. The method comprises depositing and patterning a first mask on a silicon wafer to define desired first areas on the wafer to be etched. First trenches are etched on parts of the wafer not covered by the first mask. The first trenches are filled with a deposit layer. A part of the deposit layer is removed on desired second areas to be etched and a remainder is left on areas to function as a second mask to define final structures. Parts of the wafer on the desired second areas is etched, and the second mask is removed. A gyroscope or accelerator can be manufactured by dimensioning the structures.

Description

BACKGROUND[0001]1. Field[0002]The invention is concerned with a method of creating MEMS structures by selectively etching a silicon wafer that is patterned by using a masking layer for defining the structural features of a MEMS device. The invention is also concerned with the use of the method[0003]2. Description of the Related Art[0004]Basically, a MEMS device has moving elements under the control of integrated microelectronics and contains micro-circuitry on a tiny silicon chip into which some mechanical device, such as a microsensor, and a micro actuator has been manufactured. These microsensors and microactuators constitute the functional elements of micro-electromechanical (MEMS) devices. The physical dimensions of MEMS devices can vary from below one micron to several millimeters.[0005]MEMS devices convert a measured mechanical signal into an electrical signal and MEMS sensors measure the mechanical phenomenon and the electronics then process the information derived from the s...

Claims

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Application Information

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IPC IPC(8): B81C1/00
CPCB81C1/00531B81C1/00412B81C1/00404B81B3/00B81C1/00396B81C1/00611G01C19/5656G01C19/5663B81C1/00373
Inventor TORKKELI, ALTTI
Owner MURATA MFG CO LTD